Such a blow mold and such a blowing machine are known from FR-PS 2 646 802.
Blow molds, in which a pre-molded blank is molded by blowing with overpressure in the interior of the blow mold—that is to say, profiled out—are thereby used for the stretch blowing of pre-molded blanks for plastic bottles. The blow mold can, for example, thereby comprise two mold parts, which are supported in a rotatable manner around a common axis. By rotating around this axis, the mold parts can be sealed shut, so that a hollow cavity, in which a pre-molded blank can be molded by blowing, forms within the interior of the blow mold bounded by the two mold parts.
Since relatively high pressures, such as 40 bar, for example, are used in stretch blowing, it is necessary that both of the mold parts attached in a swivelable manner be able to be locked in their sealed condition, so that they can resist the strong internal pressures.
In accordance with FR-PS 2 646 802, a projection with a penetrating aperture is thereby provided on one lateral end of one of the mold parts, and an additional, vertically displaced projection is attached to the lateral surface of the second mold part that is positioned directly opposite to it in the closed condition, which projection accommodates a pin projecting out vertically, which can be inserted into or protrude out from the aperture in the projection of the first mold part. The locking of the mold parts in the blowing machine is thereby brought about in the manner of a trailer coupling by means of a stroke movement by several pins attached to a common activating bar.
This solution is, in any event, expensive in mechanical terms since, in addition to a horizontal movement—that is to say, a horizontal rotating of the two mold parts for opening and closing, for example—, a vertical movement of the activating bar with the pins is still additionally necessary in order to achieve the locking of the two mold parts by engaging the vertically projecting pins of one mold part in the apertures provided in the other mold part.
In an alternative manner, U.S. Pat. No. 3,601,858 proposes providing an anchor-like locking element on one of the mold parts, which element has areas projecting upwardly or downwardly on its end assigned to the other mold part.
Furthermore, two locking hooks, which are acted on by swivel arms and can be rotated by these swivel arms in such a manner that, in one locking position, they encompass the projecting areas of the anchor element attached to the other mold part so that this is set firmly in its position, are provided on the other mold part. Through the swiveling of the locking hooks around their swivel arms, the contact of the hook with the locking anchor of the other mold part can be ended again, and both of the mold parts can thereby be opened.
In any event, this structure, which involves providing hook-shaped elements with corresponding swivel arms which can be retracted relative to one another, can also only be carried out in relatively expensive mechanical terms.